Their results show the range in water D/H ratio of the carbonaceous chondrites is ~0.2x10 -4 to ~7.3x10 -4. The remnants of ice preserved in these chondrites are in the form of hydrated silicates, such as clays. They analyzed bulk hydrogen, carbon, and nitrogen elemental and isotopic compositions of 86 samples of carbonaceous chondrite meteorites and inferred the initial water D/H ratios. That's part of the reason why researchers have been collecting hydrogen isotopic data on a variety of planetary materials to compare with Earth's D/H ratio to help determine the contributions of water delivered to Earth by (outer Solar System) comets versus (inner Solar System) water-bearing carbonaceous asteroids.Ĭonel Alexander (Carnegie Institution of Washington) and colleagues from the US and Canada have added more data to the table. Bodies formed in the same source regions and at similar times should have accreted ice with similar D/H ratios. In our Solar System, the water D/H ratio is a kind of fingerprint of where icy planetesimals formed the ratio increases with increasing formation distance from the Sun. As a reference, the measured D/H in Earth's standard mean ocean water ( SMOW) is 1.558x10 -4. Its nucleus contains a proton and a neutron hydrogen's nucleus contains only a proton. Deuterium is an isotope of hydrogen that's also called heavy hydrogen. The answers are relevant to planetary accretion models and also to dynamical models that seek to explain how materials moved and mixed in the early Solar System.Ī vital piece of information in this work, the detail that connects Earth's water to extraterrestrial bodies, is the water deuterium/hydrogen ratio (D/H). Sorting out the details of water delivery to Earth as well as the larger issue of the different inventories of water ice in the early Solar System are hot research topics. Water, Carbonaceous Chondrites, and Earthīesides the water we assume was in the original materials that accreted to form Earth, theory holds that water has since been added to Earth by impacting comets and pieces of asteroids-especially the chemically primitive carbonaceous chondrites.Īlong with the water, we know from laboratory studies of extraterrestrial materials that comets and asteroids contain prebiotic organic chemicals and amino acids, which only heightens our interest in them as carriers of the ingredients for life.
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